This invention relates generally to displacement sensors. This invention relates particularly to a displacement sensor that includes a pair of multiple layer spiral-wound optical fiber coils on opposite sides of a flexural disk with the optical fiber coils being included in an interferometer. Still more particularly, this invention relates to a displacement sensor that includes a peripheral ring that has fiber routing slots around the edge of the flexural disk.
A fiber optic displacement sensor according to the present invention comprises a support base having a mounting post extending,therefrom. A flexural disk is connected to the mounting post, and a first spiral wound optical fiber coil is formed on the first side of the flexural disk. A second spiral wound optical fiber coil is formed on the second side of the flexural disk. Optical fiber leads extend from both the inner and outer diameters of the optical fiber coils. An optical coupler is arranged to couple optical signals between the optical fiber lead extending from each of the coils. The ends of the remaining leads are mirrored so that the combination of the optical fiber coils, leads and coupler forms a Michelson interferometer.
An inertia ring is connected to the periphery of the flexural disk. The inertia ring has a plurality of peripheral slots therein for routing the optical fiber leads from the first and second optical fiber coils to the optical coupler and to locations where the mirrored ends are secured.
The inertia ring preferably includes curved oppositely facing side edges with the plurality of peripheral slots being formed between the curved side edges. The curved side edges are formed such that the optical fiber leads may be spiral wound thereon between the first and second coils and the peripheral slots to prevent damage to the optical fiber leads from sharp bends.
The plurality of slots in the inertia ring are preferably arranged to allow differing lengths of fiber to be wound circumferentially, as required, in different depth slots to accommodate mismatches in optical fiber lead lengths. This allows both the fiber leads from the first and second fiber coils to ultimately exit the coil assembly together and take the same path to the coupler to provide improved common mode rejection of extraneous environmentally-induced phase shifts.
An appreciation of the objectives of the present invention and a more complete understanding of its structure and method of operation may be had by studying the following description of the preferred embodiment and by referring to the accompanying drawings.